////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1999-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include <map>

extern "C"
{
#if defined (HAVE_DLOPEN_API)
#  if defined (HAVE_DLFCN_H)
#    include <dlfcn.h>
#  else
extern void * dlopen (const char *, int);
extern const char * dlerror (void);
extern void * dlsym (void *, const char *);
extern int dlclose (void *);
#  endif
#elif defined (HAVE_LOADLIBRARY_API)
#  define WIN32_LEAN_AND_MEAN 1
#  include <windows.h>
#  include <psapi.h>
#endif
}

#include "file-ops.h"
#include "file-stat.h"
#include "lo-error.h"
#include "oct-shlib.h"
#include "str-vec.h"

#if defined (HAVE_LOADLIBRARY_API)
#  include "lo-sysdep.h"
#endif

namespace octave
{
  dynamic_library::dynlib_rep::dynlib_rep (const std::string& f)
    : m_count (1), m_fcn_names (), m_file (f), m_time_loaded (),
      m_search_all_loaded (false)
  {
    s_instances[f] = this;

    if (is_out_of_date ())
      (*current_liboctave_warning_with_id_handler)
        ("Octave:warn-future-time-stamp",
         "timestamp on file %s is in the future", m_file.c_str ());
  }

  bool
  dynamic_library::dynlib_rep::is_out_of_date (void) const
  {
    sys::file_stat fs (m_file);
    return (fs && fs.is_newer (m_time_loaded));
  }

  void
  dynamic_library::dynlib_rep::fake_reload (void)
  {
    // We can't actually reload the library, but we'll pretend we did.
    sys::file_stat fs (m_file);
    if (fs && fs.is_newer (m_time_loaded))
      {
        m_time_loaded = fs.mtime ();

        (*current_liboctave_warning_with_id_handler)
          ("Octave:library-reload",
           "library %s not reloaded due to existing references", m_file.c_str ());
      }
  }

  dynamic_library::dynlib_rep *
  dynamic_library::dynlib_rep::get_instance (const std::string& f, bool fake)
  {
    dynlib_rep *retval = nullptr;
    std::map<std::string, dynlib_rep *>::iterator p = s_instances.find (f);
    if (p != s_instances.end ())
      {
        retval = p->second;
        retval->m_count++;
        if (fake)
          retval->fake_reload ();
      }
    else
      retval = new_instance (f);

    return retval;
  }

  std::list<std::string>
  dynamic_library::dynlib_rep::function_names (void) const
  {
    std::list<std::string> retval;

    for (const auto& p : m_fcn_names)
      retval.push_back (p.first);

    return retval;
  }

  void
  dynamic_library::dynlib_rep::add_fcn_name (const std::string& name)
  {
    auto p = m_fcn_names.find (name);

    if (p == m_fcn_names.end ())
      m_fcn_names[name] = 1;
    else
      ++(p->second);
  }

  bool
  dynamic_library::dynlib_rep::remove_fcn_name (const std::string& fcn_name)
  {
    bool retval = false;

    auto p = m_fcn_names.find (fcn_name);

    if (p != m_fcn_names.end () && --(p->second) == 0)
      {
        m_fcn_names.erase (fcn_name);
        retval = true;
      }

    return retval;
  }

  std::map<std::string, dynamic_library::dynlib_rep *>
    dynamic_library::dynlib_rep::s_instances;

  dynamic_library::dynlib_rep dynamic_library::s_nil_rep;

#if defined (HAVE_DLOPEN_API)

  class
  octave_dlopen_shlib : public dynamic_library::dynlib_rep
  {
  public:

    octave_dlopen_shlib (const std::string& f);

    // No copying!

    octave_dlopen_shlib (const octave_dlopen_shlib&) = delete;

    octave_dlopen_shlib& operator = (const octave_dlopen_shlib&) = delete;

    ~octave_dlopen_shlib (void);

    void * search (const std::string& name,
                   const dynamic_library::name_mangler& mangler
                     = dynamic_library::name_mangler ());

    // FIXME: this is possibly redundant because failure to open a library will
    // normally throw an exception, avoiding the construction of an invalid
    // library.  Leave it here for possible future use.

    bool is_open (void) const
    {
      return (m_search_all_loaded || m_library != nullptr);
    }

  private:

    void *m_library;
  };

  octave_dlopen_shlib::octave_dlopen_shlib (const std::string& f)
    : dynamic_library::dynlib_rep (f), m_library (nullptr)
  {
    int flags = 0;

    // Use RTLD_NOW to resolve all symbols before dlopen returns.
    // By using this option, dlopen will detect errors and Octave
    // won't exit if there are unresolved symbols in the file we are
    // loading, and we may even get a useful diagnostic.
#  if defined (RTLD_NOW)
    flags |= RTLD_NOW;
#  endif

    // Use RTLD_GLOBAL to export symbols from loaded objects so they are
    // available to other subsequently loaded libraries.
#  if defined (RTLD_GLOBAL)
    flags |= RTLD_GLOBAL;
#  endif

    if (m_file.empty ())
      {
        m_search_all_loaded = true;
        return;
      }

    m_library = dlopen (m_file.c_str (), flags);

    if (! m_library)
      {
        const char *msg = dlerror ();

        if (msg)
          (*current_liboctave_error_handler) ("%s: failed to load: %s",
                                              m_file.c_str (), msg);
        else
          (*current_liboctave_error_handler) ("%s: failed to load",
                                              m_file.c_str ());
      }
  }

  octave_dlopen_shlib::~octave_dlopen_shlib (void)
  {
    if (m_library)
      dlclose (m_library);
  }

  void *
  octave_dlopen_shlib::search (const std::string& name,
                               const dynamic_library::name_mangler& mangler)
  {
    void *function = nullptr;

    if (! is_open ())
      (*current_liboctave_error_handler)
        ("shared library %s is not open", m_file.c_str ());

    std::string sym_name = name;

    if (mangler)
      sym_name = mangler (name);

    if (m_search_all_loaded)
      function = dlsym (RTLD_DEFAULT, sym_name.c_str ());
    else
      function = dlsym (m_library, sym_name.c_str ());

    return function;
  }

#elif defined (HAVE_LOADLIBRARY_API)

  class
  octave_w32_shlib: public dynamic_library::dynlib_rep
  {
  public:

    octave_w32_shlib (const std::string& f);

    // No copying!

    octave_w32_shlib (const octave_w32_shlib&) = delete;

    octave_w32_shlib& operator = (const octave_w32_shlib&) = delete;

    ~octave_w32_shlib (void);

    void * search (const std::string& name,
                   const dynamic_library::name_mangler& mangler
                     = dynamic_library::name_mangler ());

    void * global_search (const std::string& sym_name);

    bool is_open (void) const
    {
      return (m_search_all_loaded || m_handle != nullptr);
    }

  private:

    HINSTANCE m_handle;
  };

  octave_w32_shlib::octave_w32_shlib (const std::string& f)
    : dynamic_library::dynlib_rep (f), m_handle (nullptr)
  {
    if (f.empty())
      {
        m_search_all_loaded = true;
        return;
      }

    std::string dir = sys::file_ops::dirname (f);
    std::wstring wdir = sys::u8_to_wstring (dir);
    SetDllDirectoryW (dir.empty ()
                      ? nullptr : wdir.c_str ());

    std::wstring wfile = sys::u8_to_wstring (m_file);
    m_handle = LoadLibraryW (wfile.c_str ());

    SetDllDirectoryW (nullptr);

    if (! m_handle)
      {
        DWORD last_error = GetLastError ();

        wchar_t *error_text = nullptr;
        FormatMessageW (FORMAT_MESSAGE_FROM_SYSTEM |
                        FORMAT_MESSAGE_ALLOCATE_BUFFER |
                        FORMAT_MESSAGE_IGNORE_INSERTS,
                        nullptr, last_error,
                        MAKELANGID (LANG_NEUTRAL, SUBLANG_DEFAULT),
                        reinterpret_cast <wchar_t *> (&error_text), 0, nullptr);

        std::ostringstream err_str;
        err_str << "opening the library '" << m_file << "' failed (error "
                << last_error << "): ";
        if (error_text != nullptr)
          {
            err_str << sys::u8_from_wstring (error_text);
            LocalFree (error_text);
          }
        else
          err_str << "Unknown error.";

        (*current_liboctave_error_handler) ("%s", err_str.str ().c_str ());
      }
  }

  octave_w32_shlib::~octave_w32_shlib (void)
  {
    if (m_handle)
      FreeLibrary (m_handle);
  }

  void *
  octave_w32_shlib::global_search (const std::string& sym_name)
  {
    void *function = nullptr;

    HANDLE proc = GetCurrentProcess ();

    if (! proc)
      (*current_liboctave_error_handler)
        ("Unable to get handle to own process.");

    std::size_t lib_num = 64;
    std::size_t size_lib = sizeof (HMODULE);
    HMODULE *h_libs;
    DWORD bytes_all_libs;
    bool got_libs;

    // Get a list of all the libraries in own process.
    h_libs = static_cast<HMODULE *> (malloc (size_lib*lib_num));
    got_libs = EnumProcessModules (proc, h_libs, size_lib*lib_num,
                                   &bytes_all_libs);
    int ii = 0;
    while (((size_lib*lib_num) < bytes_all_libs) && ii++ < 3)
      {
        lib_num = bytes_all_libs / size_lib;
        h_libs = static_cast<HMODULE *> (realloc (h_libs, bytes_all_libs));
        got_libs = EnumProcessModules (proc, h_libs, bytes_all_libs,
                                       &bytes_all_libs);
      }

    if (got_libs)
      {
        for (std::size_t i = 0; i < (bytes_all_libs / size_lib); i++)
          {
            // Check for function in library.
            function = reinterpret_cast<void *>
                       (GetProcAddress (h_libs[i], sym_name.c_str ()));

            if (function)
              break;
          }
      }

    // Release the handle to the process.
    CloseHandle (proc);

    return function;
  }

  void *
  octave_w32_shlib::search (const std::string& name,
                            const dynamic_library::name_mangler& mangler)
  {
    void *function = nullptr;

    if (! m_search_all_loaded && ! is_open ())
      (*current_liboctave_error_handler)
        ("shared library %s is not open", m_file.c_str ());

    std::string sym_name = name;

    if (mangler)
      sym_name = mangler (name);

    if (m_search_all_loaded)
      function = global_search (sym_name);
    else
      function = reinterpret_cast<void *> (GetProcAddress (m_handle,
                                                           sym_name.c_str ()));

    return function;
  }

#endif

  dynamic_library::dynlib_rep *
  dynamic_library::dynlib_rep::new_instance (const std::string& f)
  {
#if defined (HAVE_DLOPEN_API)
    return new octave_dlopen_shlib (f);
#elif defined (HAVE_LOADLIBRARY_API)
    return new octave_w32_shlib (f);
#else
    (*current_liboctave_error_handler)
      ("support for dynamically loaded libraries was unavailable or disabled when liboctave was built");
#endif
  }
}
